Membrane proteins of normal red cells, stored red cells, and red cells from patients with certain hemolytic disorders will be studied under various conditions of in vitro incubation to elucidate changes in surface topography and composition and internal structure of the membrane. The impermeant radioactive probe, 125I-diazodiiodosulfanilic acid, chemical measurement of proteins and hemoglobin, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis will be the major techniques employed.